Coherent optical communication systems and wavelength-division-multiplexed networks require optical sources at a plurality of different wavelengths. It is also desired that such sources emit a single wavelength output.
Diffraction gratings have been used in optical sources and other optical devices for the separate purposes of linewidth narrowing and wavelength activity. For example, DBR and DRB lasers employ fixed diffraction gratings for linewidth narrowing a predetermined wavelength. However, such lasers are not dynamically tunable to other operating wavelength.